In-situ high power implant to relieve stress of a thin film

ABSTRACT

Embodiments of the present disclosure generally relate to techniques for deposition of high-density films for patterning applications. In one embodiment, a method of processing a substrate is provided. The method includes depositing a carbon hardmask over a film stack formed on a substrate, wherein the substrate is positioned on an electrostatic chuck disposed in a process chamber, implanting ions into the carbon hardmask, wherein depositing the carbon hardmask and implanting ions into the carbon hardmask are performed in the same process chamber, and repeating depositing the carbon hardmask and implanting ions into the carbon hardmask in a cyclic fashion until a pre-determined thickness of the carbon hardmask is reached.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 62/688,721 filed on Jun. 22, 2018, which is herein incorporated byreference in its entirety.

BACKGROUND Field

Embodiments of the present disclosure generally relate to thefabrication of integrated circuits. More particularly, the embodimentsdescribed herein provide techniques for deposition of high-density filmsfor patterning applications.

Description of the Related Art

Hardmasks are used to fabricate NAND and dynamic random access memory(DRAM) devices. Hardmasks are commonly used as sacrificial layers inlithographic patterning and enable, through an etch process, thepatterning of features onto one or more of the material layers of asemiconductor device. The patterned features can form, for example, thetransistors and interconnects that allow the NAND and DRAM devices tooperate.

Some important properties of a hardmask material are etch resistance andcompressive stress, for example. An ideal hardmask has a high etchresistance to an etchant used in the etch process as compared to thelayer to be etched (hereinafter, an “underlayer”). Therefore, theunderlayer can be etched at a rate much faster than the hardmask. Anideal hardmask also has a low compressive stress. Lower compressivestress eliminates undesirable substrate bow after hardmask deposition,which can make further device fabrication difficult.

In an effort to improve etch selectivity of the hardmask, high densitycarbon films and doped carbon films have been developed. One of thechallenges with these new films is that high density carbon filmsexhibit high compressive stress, which results in undesirable substratebow.

Therefore, there is a need in the art for improved methods of forming ahardmask which exhibits increased etch selectivity while maintaining orreducing the compressive stress of the hardmask material.

SUMMARY

Embodiments of the present disclosure generally relate to techniques fordeposition of high-density films for patterning applications. In oneembodiment, a method of processing a substrate is provided. The methodincludes depositing a carbon hardmask over a film stack formed on asubstrate, wherein the substrate is positioned on an electrostatic chuckdisposed in a process chamber, implanting ions into the carbon hardmask,wherein depositing the carbon hardmask and implanting ions into thecarbon hardmask are performed in the same process chamber, and repeatingdepositing the carbon hardmask and implanting ions into the carbonhardmask in a cyclic fashion until a pre-determined thickness of thecarbon hardmask is reached.

In another embodiment, a method of processing a substrate is provided.The method includes depositing a carbon hardmask over a substrate,wherein the carbon hardmask is deposited by applying a RF bias to anelectrostatic chuck upon which the substrate is positioned to generate aplasma, and while deposing the carbon hardmask over the substrate,implanting ions from the plasma into the carbon hardmask using the RFbias, wherein depositing the carbon hardmask and implanting ions intothe carbon hardmask are simultaneously performed in the same processchamber.

In yet another embodiment, a method of processing a substrate isprovided. The method includes depositing a diamond-like carbon hardmaskover a film stack formed on a substrate by applying a first RF powerhaving a first power level to an electrostatic chuck via a firstelectrode, wherein the substrate is positioned on the electrostaticchuck in which the first electrode is disposed, implanting ions into thediamond-like carbon hardmask, wherein depositing the diamond-like carbonhardmask and implanting ions into the diamond-like carbon hardmask areperformed in the same process chamber, repeating depositing thediamond-like carbon hardmask and implanting ions into the diamond-likecarbon hardmask in a cyclic fashion until a pre-determined thickness ofthe diamond-like carbon hardmask is reached, patterning the diamond-likecarbon hardmask, etching the film stack using the patterned diamond-likecarbon hardmask, and removing the diamond-like carbon hardmask.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description ofthe embodiments, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIGS. 1A and 1B are flow diagrams setting forth a method for forming ahardmask on a film stack in accordance with embodiments of the presentdisclosure.

FIGS. 2A-2F are schematic, cross-sectional views of a stack illustratinga hardmask formation sequence according to the method of FIGS. 1A and1B.

FIGS. 3A and 3B are flow diagrams setting forth a method for depositinga hardmask on a film stack in accordance with embodiments of the presentdisclosure.

FIG. 4 is a graph depicting (1) stress as a function of bias power and(2) density as a function of bias power for a diamond-like carbon layerformed in accordance with one or more embodiments of the presentdisclosure.

FIG. 5 is a graph depicting stress as a function of implant dosage for adiamond-like carbon layer formed in accordance with one or moreembodiments of the present disclosure.

FIG. 6 is a schematic cross sectional view of an exemplary processingwhich may be used to practice the methods set forth herein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

Embodiments described herein include improved methods of fabricatingcarbon films with high-density (e.g., >1.8 g/cc), high modulus(e.g., >150 GPa), and low stress (e.g., <−500 MPa). Particularly, anin-situ deposition-implantation process is disclosed to form a highdensity carbon film with increased hardness and reduced stress in adeposition chamber. The in-situ deposition-implantation process can beperformed in a cyclic or simultaneous fashion to allow the carbon filmto form with any target thickness without being limited to ionpenetration threshold, which would otherwise have been encountered ifthe deposition and implantation processes were performed ex-situ. Thecarbon films fabricated according to the embodiments described hereinare amorphous in nature and have a higher etch selectivity with muchgreater modulus (e.g., >150 GPa) along with lower stress (<−500 MPa)than conventional patterning films. The carbon films fabricatedaccording to the embodiments described herein not only have a low stressbut also have a high sp³ carbon content (e.g., diamond-like films). Ingeneral, the deposition process described herein is also fullycompatible with current integration schemes for hardmask applications.

While high density carbon films are discussed in this disclosure, it iscontemplated that various embodiments of this disclosure can also beused to improve film stress, density, or Young's modulus of any films.In addition, it is contemplated that aspects of the present disclosureare applicable to any deposition processes or patterning schemes, suchas a self-aligned triple patterning (SATP) process, a self-alignedquadruple patterning (SAQP) process, a via/hole shrink process, a backend of line (BEOL), etc., that utilize a hardmask or protectivesacrificial layer, as employed in various semiconductor processes suchas NAND flash application, DRAM application, or CMOS application, etc.

Embodiments described herein will be described below in reference to aPECVD process that can be carried out using any suitable thin filmdeposition system. Examples of suitable systems include the CENTURA®systems which may use a DXZ® processing chamber, PRECISION 5000®systems, PRODUCER® systems, PRODUCER® GT™ systems, PRODUCER® XPPrecision™ systems, PRODUCER® SE™ systems, Sym3® processing chamber, andMesa™ processing chamber, all of which are commercially available fromApplied Materials, Inc., of Santa Clara, Calif. Other tools capable ofperforming PECVD processes may also be adapted to benefit from theembodiments described herein. In addition, any system enabling the PECVDprocesses described herein can be used.

FIGS. 1A and 1B are flow diagrams setting forth a method 100 for forminga hardmask on a film stack disposed on a substrate in accordance withembodiments of the present disclosure. FIGS. 2A-2F are schematic,cross-sectional views of a stack 200 illustrating a hardmask formationsequence according to the method 100. The hardmask may be a diamond-likecarbon layer described above, and can be utilized to manufacturestair-like structures in the film stack for three dimensionalsemiconductor devices, or any suitable device manufacturingapplications. It should also be understood that the operations depictedin FIGS. 1A and 1B may be performed simultaneously and/or in a differentorder than the order depicted in FIGS. 1A and 1B.

The method 100 begins at operation 102 by positioning a stack, such as astack 200 depicted in FIG. 2A, into a process chamber, such as a PECVDchamber. The stack 200 may be positioned on an electrostatic chuckdisposed in the PECVD chamber. However, any suitable substrate supportmay be used to replace the electrostatic chuck. Once the stack 200 ispositioned on the electrostatic chuck, a chucking voltage (eitherconstant or pulsed) is applied to the electrostatic chuck to clamp thesubstrate 202 to the electrostatic chuck. The stack 200 includes asubstrate 202 and one or more layers disposed thereon. In an example asshown, the substrate 202 has a film stack 204 disposed thereon. Thesubstrate 202 may be a silicon-based material or any suitable insulatingmaterial or conductive material as needed. For example, the substrate202 may be a material such as crystalline silicon (e.g., Si<100> orSi<111>), silicon oxide, strained silicon, silicon germanium, doped orundoped polysilicon, doped or undoped silicon substrates and patternedor non-patterned substrates silicon on insulator (SOI), carbon dopedsilicon oxides, silicon nitride, doped silicon, germanium, galliumarsenide, glass, sapphire. The substrate 202 may have variousdimensions, such as 200 mm, 300 mm, and 450 mm or other diameter, aswell as, rectangular or square panel shapes. Unless otherwise noted,embodiments and examples described herein are conducted on substrateswith a 200 mm diameter, a 300 mm diameter, or a 450 mm diameter. In theembodiment wherein a SOI structure is utilized for the substrate 202,the substrate may include a buried dielectric layer disposed on asilicon crystalline substrate. In the embodiment depicted herein, thesubstrate 202 may be a crystalline silicon substrate.

The film stack 204 may be a single layer or a number of verticallystacked layers. For example, the film stack 204 may include pairs of afirst layer (not shown) and a second layer (not shown) repeatedly formedin the film stack 204. The pairs include alternating first layers andsecond layers repeatedly formed until desired numbers of pairs of thefirst layers and the second layers are reached. The film stack 204 maybe a part of a semiconductor chip, such as a three-dimensional memorychip. In one embodiment, the film stack 204 is utilized to form multiplegate structures for a three-dimensional memory chip. In such a case, thefirst layers formed in the film stack 204 may be a first dielectriclayer and the second layers formed in the film stack 204 may be a seconddielectric layer. Suitable dielectric layers for the first layers andthe second layer may include silicon oxide, silicon nitride, siliconoxynitride, silicon carbide, silicon oxycarbide, titanium nitride,composite of oxide and nitride, at least one or more oxide layerssandwiching a nitride layer, and combinations thereof, among others. Insome embodiments, one or both of the first and second dielectric layersmay be a high-k material having a dielectric constant greater than 4.Suitable examples of the high-k materials include hafnium dioxide(HfO₂), zirconium dioxide (ZrO₂), hafnium silicon oxide (HfSiO₂),hafnium aluminum oxide (HfAlO), zirconium silicon oxide (ZrSiO₂),tantalum dioxide (TaO₂), aluminum oxide, aluminum doped hafnium dioxide,bismuth strontium titanium (BST), and platinum zirconium titanium (PZT),among others. The film stack 204 may have a total thickness betweenabout 100 Å and about 2000 Å. In one embodiment, a total thickness ofthe film stack 204 is about 3 microns to about 10 microns and will varyas technology advances.

During operation 102, several process parameters may be regulated. Inone embodiment suitable for processing a 300 mm substrate, the processpressure in the processing volume may be maintained at about 0.1 mTorrto about 10 Torr (e.g., about 2 mTorr to about 50 mTorr; or about 5mTorr to about 20 mTorr). The processing temperature and/or substratetemperature may be maintained at about −50 degrees Celsius to about 350degrees Celsius (e.g., about 0 degrees Celsius to about 50 degreesCelsius; or about 10 degrees Celsius to about 20 degrees Celsius).

At operation 104, a hydrocarbon-containing gas is flowed into theprocess chamber. The hydrocarbon-containing gas may be flowed into theprocess chamber either through a gas distribution assembly (disposed onthe top of the process chamber above the electrostatic chuck) or via asidewall of the process chamber. The hydrocarbon-containing gas mayinclude at least one hydrocarbon compound. The hydrocarbon compound canbe any liquid or gas. In one embodiment, the hydrocarbon compound is agaseous hydrocarbon. In another embodiment, the hydrocarbon compound mayinitially be a liquid, and may be delivered to the processing volume viaa vaporizer or bubbler, or other liquid precursor delivery system.

In one embodiment, the hydrocarbon compound has a general formulaC_(x)H_(y), where x has a range of between 1 and 20 and y has a range ofbetween 1 and 20. Suitable hydrocarbon compounds may include, forexample, acetylene (C₂H₂), ethylene (C₂H₄), ethane (C₂H₆), propyne(C₃H₄), propylene (C₃H₆), propane (C₃H₈), butane (C₄H₁₀), methane (CH₄),butylene (C₄H₈), butane (C₄H₁₀), pentane (C₅H₁₂), hexane (C₆H₁₄),adamantine (C₁₀H₁₆), norbornene (C₇H₁₀), or combinations thereof. C₂H₂may be advantageous due to formation of more stable intermediatespecies, which allows more surface mobility.

In one embodiment, the hydrocarbon compound is an aromatic hydrocarboncompound, such as benzene, styrene, toluene, xylene, ethylbenzene,acetophenone, methyl benzoate, phenyl acetate, phenol, cresol, furan,and the like, alpha-terpinene, cymene, 1,1,3,3,-tetramethylbutylbenzene,t-butylether, t-butylethylene, methyl-methacrylate, andt-butylfurfurylether, compounds having the formula C₃H₂ and C₅H₄,halogenated aromatic compounds including monofluorobenzene,difluorobenzenes, tetrafluorobenzenes, hexafluorobenzene, orcombinations thereof. In some cases, hydrocarbon compounds containingoxygen and halogenated precursors are not required.

In some embodiments, an inert gas, such as argon (Ar) and/or helium (He)may be supplied with the hydrocarbon-containing gas into the processchamber. Other inert gases, such as nitrogen (N₂) and nitric oxide (NO),may also be used to control the density and deposition rate of thediamond-like carbon layer.

In some embodiments, the hydrocarbon-containing gas may further includeone or more dilution gases. Suitable dilution gases may include, but arenot limited to, helium (He), argon (Ar), xenon (Xe), hydrogen (H₂),nitrogen (N₂), ammonia (NH₃), nitric oxide (NO), or combinationsthereof. Ar, He, and N₂ may be used to control the density anddeposition rate of the diamond-like carbon layer. In some cases, theaddition of N₂ and/or NH₃ can be used to control the hydrogen ratio(e.g., carbon to hydrogen ratio) of the diamond-like carbon layer.

At operation 106, a plasma is generated in the process chamber from thegas mixture to form a hardmask 206 on the film stack 204, as shown inFIG. 2B. The plasma may be generated by applying a first RF power (biasor source) to the electrostatic chuck. The first RF power may be fromabout 1 Kilowatts to about 10 Kilowatts at a frequency of about 0.4 MHzto about 300 MHz, for example about 11 MHz to about 60 MHz. In oneembodiment, the first RF power is provided at about 2 Kilowatts and afrequency of about 13.56 MHz. The first RF power may be provided from anRF power generator to the electrostatic chuck via a first electrodedisposed in the electrostatic chuck. In some cases, the first electrodemay also be in electronic communication with a chucking power source,which provides direct current (DC) power to electrostatically secure thesubstrate 202 to the upper surface of the electrostatic chuck.

Additionally or alternatively, the first RF power may be applied to anupper electrode, such as a showerhead that is disposed at the top of theprocess chamber opposing the electrostatic chuck. In some embodiments,the first RF power may be applied to at least one of the upperelectrode, the bottom electrode (e.g., the first electrode), and an ICPcoil which surrounds a portion of the process chamber. The ICP coil maybe used to form the plasma or to tune the uniformity of the plasmawithin the process chamber. The top electrode, the bottom electrode, andthe ICP coil can be powered simultaneously, or two of the three can bepowered simultaneously, depending on the power scheme. The applied RFfrequency can range from a few hundreds of kHz to tens of MHz. Multiplefrequencies could also be applied to the top electrode or bottomelectrode to optimize ion fluxes and energy incident onto the substrate

In one embodiment, the hardmask 206 is a diamond-like carbon film asdiscussed above. The hardmask 206 may be deposited by a blanketdeposition process over the film stack 204. It is noted that thehardmask 206 may be formed on any surfaces or any portion of thesubstrate 202 with or without the film stack 204 present on thesubstrate 202. In some embodiments, the process conditions establishedduring operation 102 are maintained during operations 104 and 106. Inone embodiment, the pressure of the process chamber during formation ofthe hardmask 206 is maintained at about 2 mTorr to about 20 mTorr.

At operation 108, an ion implantation process is performed in theprocess chamber to treat the hardmask 206, as shown in FIG. 2C. In oneembodiment, the ion implantation process is performed in-situ in thesame process chamber where the deposition process of the hardmask 206(i.e., operation 106) was performed. During operation 108, the flow ofthe hydrocarbon-containing gas is discontinued while the inert gasand/or the dilution gas supplied during operation 104 may be maintained.Meanwhile, the first RF power applied to the electrostatic chuck duringoperation 106 is reduced to a minimum level that is sufficient tosustain the plasma (i.e., the plasma is continuous during operation 106and 108). For example, the first RF power may be reduced from about 2Kilowatts to about 200 Watts.

The ion implantation process is performed by implanting ions, such asions from the continuous flow of the inert gas, and ions from thehydrocarbon-containing gas that is still remaining in the plasma). Insome embodiments, the ions are implanted into the hardmask 206 using adirect current (DC) bias voltage. The DC bias voltage is overlaid on topof the reduced first RF power. Particularly, the DC bias voltage driveshigh mono-energetic ions into the hardmask 206. The DC bias voltage maybe provided to the electrostatic chuck via a second electrode. Thesecond electrode may be disposed in the electrostatic chuck and inelectrical communication with a DC power source that provides the biasvoltage to the second electrode. Alternatively, the DC bias voltage maybe provided to the first electrode from the chucking power source. Inany case, the DC bias voltage may be between about 2 Kilovolts and about15 Kilovolts. In one embodiment, the DC bias voltage is between about 5Kilovolts and about 12 Kilovolts, for example about 8 Kilovolts. Sincethe DC bias voltage is high, the DC bias voltage can be pulsed duringthe ion implantation process. In various embodiments, the pulse width ofthe DC bias voltage may be of the order of about 1 microsecond to about1 millisecond. In some embodiments, the DC bias voltage is applied at apulse frequency of 10 Hz to about 10 kHz with a pulse width of about 5microseconds to about 30 milliseconds.

In some embodiments, the ions are implanted into the hardmask 206 usinga second RF power (bias or source). Likewise, the second RF power isoverlaid on top of the reduced first RF power. The second RF power maybe provided from an RF power generator to the electrostatic chuck via athird electrode disposed in the electrostatic chuck. The second RF powermay be from about 1 Kilowatts to about 10 Kilowatts at a frequency ofabout 0.4 MHz to about 300 MHz, for example about 11 MHz to about 60MHz. In one embodiment, the first RF power is provided at about 2Kilowatts and a frequency of about 13.56 MHz. The second RF power can bepulsed during the ion implantation process. For example, the second RFpower can be pulsed with a duty cycle in a range from about 10% to about80% with a frequency of about 1 Hz to about 50 kHz.

In cases where the second RF power is used and the depositing speciesalso acts as the implanting species (e.g., H₂ from thehydrocarbon-containing gas), the reduced first RF power and the secondRF power may be offset temporally so that the reduced first RF power andthe pulsed second RF power is synchronous or non-synchronous, therebyseparating the deposition phase and treatment phase (i.e., ionimplantation). For example, when the second RF power and the reducedfirst RF power are both on, ions are accelerated causing bombardment ofthe hardmask 206 to occur, and the deposition of the hardmask 206 may beminimized because a majority of the film growth comes from the primaryplasma (e.g., first RF power) that is being operated at the low level(e.g., 200 Watts). Therefore, the ion implantation dominates. When thesecond RF power is pulsed and the reduced first RF power is on, thedeposition of the hardmask 206 is increased and becomes the dominatingprocess. Therefore, the film deposition dominates.

Regardless of whether the ion implantation process uses the DC biasvoltage or the second RF power, little or no deposition of hardmask 206will occur because the flow of the deposition gas (i.e.,hydrocarbon-containing gas) is turned off. Therefore, the pulsing of theDC bias voltage or the pulsed second RF power separates the depositionphase and the treatment phase (i.e., ion implantation process), makingthe formation and treatment of the hardmask 206 a cyclic deposit-treatprocess. During the ion implantation process, the ions from thecontinuous flow of the inert gas, such as argon or helium ions, and ionsfrom the hydrocarbon-containing gas remaining in the plasma, areattracted or driven by the DC bias voltage or the second RF power andmoved forward to the hardmask 206. The DC bias voltage or the second RFpower serves to treat the hardmask 206 by bombarding the surface of thehardmask 206 with the ions. As a result, the stress in the depositedhardmask 206 is reduced.

The ion implantation process may be performed until the implanted ionsreach a penetration threshold, which is due to implanted ions graduallylosing energy as implanted ions travel through the hardmask 206. Thepenetration threshold may be determined by the depth of penetration ofions. Alternatively, the ion implantation process may be performed untila predetermined implantation depth is reached. The predeterminedimplantation depth or the ion penetration threshold may be in a rangebetween 10 nanometers and 1 micrometer, which may vary depending on thetype and size of the ions and the bias voltage utilized to energize theions 207.

The implant energy may be between about 0.5 keV and about 60 keV, forexample about 6 keV to about 45 keV, depending on the depth ofimplantation desired. The ion dosage may be in a range from about 1×10¹³cm⁻² to about 1×10¹⁷ cm⁻², for example about 5×10¹⁶ cm⁻². The extremelylow pressure (e.g., 2 mTorr to about 20 mTorr) enables very highenergetic ions to treat/implant the surface of the hardmask 206. Withoutbeing bound by any particular theory, it is believed that the implantedions can abstract residual hydrogen atoms from the danglingcarbon-hydrogen bonds of the hardmask 206 and form a carbide structurewithin the hardmask 206. The carbide structure exhibits increasedhardness when compared to un-treated hardmask. It is also believed thatthe implanted ions occupy interstitial voids present within the hardmask206, which can result in an increased density of the hardmask 206. Theincreased density further increases the mechanical integrity of thehardmask 206. The increased hardness and density of the hardmask 206 canprovide a mechanically robust hardmask 206, which in turn leads toimproved etch selectivity and reduced internal stress. As a result,undesirable substrate deformation is eliminated.

The in-situ deposition-implantation process is beneficial because theimplantation process occurs in the same process chamber where thehardmask deposition was occurred. Therefore, the hardmask 206 can bedeposited and treated without having to break the vacuum and transfer toan ex-situ implantation tool. As a result, the overall throughput isimproved and the cost associated with ex-situ implantation tools isreduced. In addition, since the implanted ions have a penetrationthreshold, the thickness of the hardmask that are treatable ex-situ islimited. With the in-situ deposition/ion implantation process, thedeposition and treatment of the hardmask can be performed in a cyclicfashion to tailor the hardmask to potentially any target thickness inthe same process chamber.

At operation 110, a decision is made as to determine whether thedeposited hardmask 206 that has been treated reaches a target thickness.The hardmask 206 may have a target thickness corresponding to thesubsequent etching requirements of the film stack 204. In one example,the target thickness of the hardmask 206 is between about 0.5 μm andabout 1.5 μm, such as about 1.0 μm. If the target thickness of thehardmask 206 has not been reached, another cycle of deposition/ionimplantation process (e.g., operations 104, 106 and 108) may beperformed before the thickness of the treated hardmask 206 is againcompared to the target thickness. In some embodiments where theimplanted ions reach predetermined implantation or penetration depth butthe hardmask 206 has not yet reached the desired thickness, anothercycle of deposition/ion implantation process (e.g., operations 104, 106and 108) can be performed before the thickness of the treated hardmask206 is again compared to the target thickness. The cyclic process ofin-situ hardmask deposition and ion implantation is repeated until thedeposited hardmask 206 reaches the target thickness.

At operation 112, once the hardmask 206 reaches the target thickness, apatterned photoresist layer 208 is formed over the treated hardmask 206,as shown in FIG. 2D. Features or patterns may be transferred to thephotoresist 208 from a photomask utilizing an energy source, such aslight energy. In one embodiment, the photoresist is a polymeric materialand the patterning process is performed by a 193 nm immersionphotolithography process, or other similar photolithography process.Similarly, lasers may also be utilized to perform the patterningprocess.

At operation 114, the treated hardmask 206 is patterned by, for example,a photolithography and one or more etch processes, to transfer thefeatures from the photoresist 208 to the hardmask 206, as shown in FIG.2E. The etching process may be performed in any suitable etch chamber,such as a plasma etch chamber. Thereafter, the photoresist layer 208 isremoved by any suitable process, such as an ashing process or a wet etchprocess.

At operation 116, the film stack 204 is etched using the patternedhardmask 206, as shown in FIG. 2F. The etching of the film stack 204 maybe performed in any suitable process chamber, such as a plasma etchchamber. Etchants, such as fluorocarbons, may be used to remove theexposed portions of the film stack 204. The active species of theetchants are selective so that they are substantially unreactive withthe implanted ions of the hardmask 206. Thus, the etchants are selectivefor the film stack 204. Suitable examples of etchants may include, butare not limited to, CF₄, CHF₃, HBr, BCl₃, or Cl₂. The etchants may beprovided to with an inert carrier gas. The hardmask 206 is then removedusing any suitable hardmask removal process. For example, an oxygenplasma may be utilized to remove the hardmask 206. The resulting stack200 includes the film stack 204 having a feature, such as a high aspectratio feature, formed therein. The resulting stack 200 may then besubjected to further processing to form a functional semiconductordevice.

FIGS. 3A and 3B illustrate a flow diagram of a method 300 for depositinga hardmask on a film stack disposed on a substrate in accordance withembodiments of the present disclosure. The method 300 can be used toprocess the stack 200 as shown in FIGS. 2A-2F. Therefore, the method 300will be described with respect to FIGS. 2A-2F. Likewise, the depositedhardmask may be a diamond-like carbon layer as described above, and canbe utilized to manufacture stair-like structures in the film stack forthree dimensional semiconductor devices, or any suitable devicemanufacturing applications. It should also be understood that theoperations depicted in FIGS. 3A and 3B may be performed simultaneouslyand/or in a different order than the order depicted in FIGS. 3A and 3B.

Operations 302 and 304 of the method 300 are similar to operations 102and 104, and thus will not be described for the sake of brevity. Assuch, the stack 200 is formed with a film stack 204 deposited over asubstrate 202, as shown in FIG. 2A. At operation 306, a simultaneousprocess of a hardmask deposition and ion implantation treatment isperformed in the process chamber to form a hardmask 206 on the filmstack 204, as shown in FIG. 2B. The simultaneous process may beperformed by generating a plasma in the process chamber from the gasmixture (e.g., a hydrocarbon-containing gas and inert gas/dilution gas)to form a layer of the hardmask 206 over the film stack 204. The plasmamay be generated at the substrate level by applying a high voltage RFbias to the electrostatic chuck. The high voltage RF bias may be in arange from about 1 Kilowatts to about 15 Kilowatts at a frequency ofabout 0.4 MHz to about 300 MHz, for example about 11 MHz to about 60MHz. In one embodiment, the high voltage RF bias is provided at about 8Kilowatts and a frequency of about 13.56 MHz. The high voltage RF biasmay be provided from an RF power generator to the electrostatic chuckvia a third electrode disposed in the electrostatic chuck.

While depositing the hardmask 206 over the film stack 204, the highvoltage RF bias applied to the electrostatic chuck can also serve as animplant energy to attract ions from the gas mixture (i.e.,hydrocarbon-containing gas, inert gas/dilution gas) moving towards thegrowing hardmask 206. Therefore, an ion implantation treatment of thehardmask 206 is performed concurrently with the hardmask deposition, asshown in FIG. 2C. Ions are attracted and accelerated by the high voltageRF bias to bombard the surface of the hardmask 206, thereby reducing thestress of the hardmask 206.

In some embodiments, a DC bias voltage may be additionally applied tothe electrostatic chuck to facilitate the ion implantation treatment.Ions from the gas mixture (i.e., hydrocarbon-containing gas, inertgas/dilution gas) can be attracted and accelerated by the DC biasvoltage to bombard the surface of the hardmask 206, thereby reducing thestress of the hardmask 206. The DC bias voltage can be provided to theelectrostatic chuck via the second electrode, which may be disposed inthe electrostatic chuck and in electrical communication with a DC powersource, as discussed above with respect to FIGS. 1A and 1B.Alternatively, the DC bias voltage may be provided to the firstelectrode from the chucking power source. The bias voltage may bebetween about 1 Kilovolts to about 15 Kilovolts. In one embodiment, theDC bias voltage is between about 2 Kilovolts and about 6 Kilovolts. Inanother embodiment, the bias voltage is between about 8 Kilovolts andabout 10 Kilovolts. Similar to operation 108, the implant energy may bebetween about 0.5 keV and about 60 keV, for example about 6 keV to about45 keV, depending on the depth of implantation desired. The ion dosagemay be in a range from about 1×10¹³ cm⁻² to about 1×10¹⁷ cm⁻², forexample about 5×10¹⁶ cm⁻².

In any case, the flow of the gas mixture (e.g., hydrocarbon-containinggas and inert gas/dilution gas) is continuous throughout the operation308. Therefore, the depositing species (e.g., ions or neutral species ofcarbon, hydrogen, etc.) used for hardmask deposition can also functionas implanting species for ion implantation treatment. The in-situprocess of the hardmask deposition and ion implantation treatmentenables the hardmask 206 to be deposited and treated simultaneously andmore efficiently as compared to embodiments where hardmask depositionand ion implantation process are separated by short duty-cycle RF orpulsed DC voltage.

At operation 308, a decision is made as to determine whether thedeposited/treated hardmask 206 reaches a target thickness. The hardmask206 may have a target thickness corresponding to the subsequent etchingrequirements of the film stack 204. In one example, the target thicknessof the hardmask 206 is between about 0.5 μm and about 1.5 μm, such asabout 1.0 μm. If the target thickness of the hardmask 206 has not beenreached, another cycle of deposition/ion implantation process (e.g.,operations 304 and 306) may be performed before the thickness of thetreated hardmask 206 is again compared to the target thickness. Thein-situ simultaneous process of the hardmask deposition and ionimplantation treatment is repeated until the deposited/treated hardmask206 reaches the target thickness.

Operations 310, 312, 314, and 316 are similar to operations 112, 114,116, and 118, and thus will not be described for the sake of brevity.

FIG. 4 is a graph 400 depicting (1) stress as a function of bias power(represented by squares) and (2) density as a function of bias power(represented by dots), for a diamond-like carbon layer (e.g., hardmask)formed in accordance with one or more embodiments discussed above withrespect to FIGS. 3A and 3B. The x-axis represents the bias power (Watts)and the y-axis represents the density (g/cc) of the deposited films. Asillustrated in FIG. 4, for the most part, as bias power increases, thedensity of the as-deposited film increases. Particularly, the stress ofthe diamond-like carbon layer is lower at higher RF power/ion energy.

FIG. 5 is a graph 500 depicting stress as a function of implant dosagefor a diamond-like carbon layer (e.g., hardmask) formed in accordancewith one or more embodiments of the present disclosure. The graph 500depicts stress data of as-deposited and post ion implantation of thediamond-like carbon films using an implant energy of about 35 keV. Thex-axis represents the stress (MPa) of the deposited films and the y-axisrepresents the implant dosage (A.U). As illustrated in FIG. 5, thestress of the as-deposited film significantly decreases after ionimplantation treatment.

FIG. 6 is a schematic cross sectional view of an exemplary processingwhich may be used to practice any one or combination of the methods setforth herein. The processing chamber 600 includes a chamber lid assembly601, one or more sidewalls 602, and a chamber base 604. The chamber lidassembly 601 includes a chamber lid 606, a showerhead 607 disposed inthe chamber lid 606, and an electrically insulating ring 608, disposedbetween the chamber lid 606 and the one or more sidewalls 602. Theshowerhead 607, one or more sidewalls 602, and the chamber base 604together define a processing volume 605. A gas inlet 609, disposedthrough the chamber lid 606 is fluidly coupled to a gas source 610. Theshowerhead 607, having a plurality of openings 611 disposedtherethrough, is used to uniformly distribute processing gases from thegas source 610 into the processing volume 605. The showerhead 607 iselectrically coupled to a first power supply 612, such as an RF powersupply, which supplies power to ignite and maintain a plasma 613 of theprocessing gas through capacitive coupling therewith. In otherembodiments, the processing chamber 600 comprises an inductive plasmagenerator and the plasma is formed through inductively coupling an RFpower to the processing gas.

The processing volume 605 is fluidly coupled to a vacuum source, such asto one or more dedicated vacuum pumps, through a vacuum outlet 614,which maintains the processing volume 605 at sub-atmospheric conditionsand evacuates the processing gas and other gases therefrom. A substratesupport 615, disposed in the processing volume 605, is disposed on amovable support shaft 616 sealingly extending through the chamber base604, such as being surrounded by bellows (not shown) in the region belowthe chamber base 604. Herein, the processing chamber 600 isconventionally configured to facilitate transferring of a substrate 617to and from the substrate support 615 through an opening 618 in one ofthe one or more sidewalls 602, which is conventionally sealed with adoor or a valve (not shown) during substrate processing.

Herein, a substrate 617, disposed on the substrate support 615, ismaintained at a desired processing temperature using one or both of aheater, such as a resistive heating element 619, and one or more coolingchannels 620 disposed in the substrate support 615. Typically, the oneor more cooling channels 620 are fluidly coupled to a coolant source(not shown), such as a modified water source having relatively highelectrical resistance or a refrigerant source. In some embodiments, thesubstrate support 615 or one or more electrodes thereof 621 iselectrically coupled to a second power supply 622, such as a continuouswave (CW) RF power supply or a pulsed RF power supply, which supplies abias voltage thereto.

The processing chamber 600 further includes a system controller 630which is used to control the operation of the processing chamber 600 andimplement the methods set forth herein. The system controller 630includes a programmable central processing unit, herein the centralprocessing unit (CPU 631), that is operable with a memory 632 (e.g.,non-volatile memory) and support circuits 633. The support circuits 633are coupled to the CPU 631 and comprise cache, clock circuits,input/output subsystems, power supplies, and combinations thereofcoupled to the various components of the processing chamber 600, tofacilitate control thereof. The CPU 631 is one of any form of generalpurpose computer processor, such as a programmable logic controller(PLC), for controlling various components and sub-processors of theprocessing chamber 600. The memory 632, coupled to the CPU 631, isnon-transitory and is typically one or more of readily availablememories such as random access memory (RAM), read only memory (ROM),floppy disk drive, hard disk, or any other form of digital storage,local or remote.

Typically, the memory 632 is in the form of a computer-readable storagemedia containing instructions (e.g., non-volatile memory), that whenexecuted by the CPU 631, facilitates the operation of the processingchamber 600. The instructions in the memory 632 are in the form of aprogram product such as a program that implements the methods of thepresent disclosure. The program code may conform to any one of a numberof different programming languages. In one example, the disclosure maybe implemented as a program product stored on computer-readable storagemedia for use with a computer system. The program(s) of the programproduct define functions of the embodiments (including the methodsdescribed herein).

Thus, methods for forming a diamond-like carbon hardmask layer that maybe utilized to form semiconductor devices are provided. By utilizationof in-situ hardmask deposition-ion implantation process, the hardmasklayer can be deposited and treated without having to break the vacuumand transfer to an ex-situ implantation tool. As a result, the overallthroughput is improved and the cost associated with ex-situ implantationtools is reduced. In addition, the deposition and treatment of thehardmask can be performed in a cyclic or simultaneous fashion usingeither independent plasma sources or one high power (high voltage)plasma source to tailor the hardmask to potentially any target thicknessin the same process chamber. Furthermore, the implanted ions function toincrease the mechanical integrity and density of the hardmask whilemaintaining or reducing the internal stress of the hardmask. Theincreased mechanical integrity and density of the hardmask reduce linebending after the hardmask is etched and the maintained or reducedstress of the hardmask reduces or eliminates undesirable substratebowing or deformation. In combination, the etch selectivity of thehardmask is increased.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

The invention claimed is:
 1. A method of processing a substrate to forma carbon hardmask comprising at least two carbon hardmask layers,comprising: depositing a first carbon hardmask layer over a film stackformed on the substrate, wherein the substrate is positioned on anelectrostatic chuck disposed in a process chamber; implanting ions intothe carbon hardmask layer, wherein depositing the carbon hardmask layerand implanting ions into the carbon hardmask are performed in the sameprocess chamber; and without the substrate leaving the process chamber,repeating depositing the one or more carbon hardmask layers andimplanting ions into the carbon hardmask layer in a cyclic fashion untila pre-determined thickness of the carbon hardmask is reached.
 2. Themethod of claim 1, wherein depositing the carbon hardmask is performedby applying a first RF power having a first power level to theelectrostatic chuck via a first electrode disposed in the electrostaticchuck.
 3. The method of claim 2, wherein the first RF power is in arange of about 1 Kilowatts to about 10 Kilowatts at a frequency of about0.4 MHz to about 300 MHz.
 4. The method of claim 2, wherein implantingions into the carbon hardmask further comprising: after depositing thecarbon hardmask over the film stack, discontinuing a flow of ahydrocarbon-containing gas for forming the carbon hardmask; and reducingthe first RF power from the first power level to a second power levelthat is sufficient to sustain plasma in the process chamber.
 5. Themethod of claim 1, wherein implanting ions into the carbon hardmask isperformed by applying a DC bias voltage to the electrostatic chuck via asecond electrode disposed in the electrostatic chuck.
 6. The method ofclaim 5, wherein the DC bias voltage is in a range of about 2 Kilovoltsto about 15 Kilovolts.
 7. The method of claim 5, wherein the DC biasvoltage is provided at a pulse frequency of 10 Hz to about 10 kHz with apulse width of about 5 microseconds to about 30 milliseconds.
 8. Themethod of claim 1, wherein implanting ions into the carbon hardmask isperformed by applying a second RF power to the electrostatic chuck via athird electrode disposed in the electrostatic chuck.
 9. The method ofclaim 8, wherein the second RF power is in a range of about 1 Kilowattsto about 10 Kilowatts at a frequency of about 0.4 MHz to about 300 MHz.10. The method of claim 9, wherein the second RF power is pulsed with aduty cycle in a range from about 10% to about 80%.
 11. A method ofprocessing a substrate, comprising: depositing a carbon hardmask over afilm stack formed on the substrate, wherein the substrate is positionedon an electrostatic chuck disposed in a process chamber; implanting ionsinto the carbon hardmask, wherein depositing the carbon hardmask andimplanting ions into the carbon hardmask are performed in the sameprocess chamber; repeating depositing the carbon hardmask and implantingions into the carbon hardmask in a cyclic fashion until a pre-determinedthickness of the carbon hardmask is reached; and after depositing thecarbon hardmask over the film stack, discontinuing a flow of ahydrocarbon-containing gas for forming the carbon hardmask; and reducingthe first RF power from the first power level to a second power levelthat is sufficient to sustain plasma in the process chamber.
 12. Themethod of claim 11, wherein depositing the carbon hardmask is performedby applying a first RF power having a first power level to theelectrostatic chuck via a first electrode disposed in the electrostaticchuck.
 13. The method of claim 12, wherein the first RF power is in arange of about 1 Kilowatts to about 10 Kilowatts at a frequency of about0.4 MHz to about 300 MHz.
 14. The method of claim 11, wherein implantingions into the carbon hardmask is performed by applying a DC bias voltageto the electrostatic chuck via a second electrode disposed in theelectrostatic chuck.
 15. The method of claim 14, wherein the DC biasvoltage is in a range of about 2 Kilovolts to about 15 Kilovolts. 16.The method of claim 14, wherein the DC bias voltage is provided at apulse frequency of 10 Hz to about 10 kHz with a pulse width of about 5microseconds to about 30 milliseconds.
 17. The method of claim 11,wherein implanting ions into the carbon hardmask is performed byapplying a second RF power to the electrostatic chuck via a thirdelectrode disposed in the electrostatic chuck.
 18. The method of claim17, wherein the second RF power is in a range of about 1 Kilowatts toabout 10 Kilowatts at a frequency of about 0.4 MHz to about 300 MHz. 19.The method of claim 18, wherein the second RF power is pulsed with aduty cycle in a range from about 10% to about 80%.